Some liquid crystal display devices include, as backlights for illuminating liquid crystal display panels from backsides, planar light sources in which light sources such as LEDs (Light Emitting Diodes) are arranged. Such a backlight is different from an edgelight-type backlight using a light guide plate in that such a backlight illuminates a liquid crystal display panel from the backside without using a light guide plate. Such a backlight is referred to as a direct-type backlight.
Light sources used in the direct-type backlight are required to be reduced in number in order to reduce costs, and therefore a wider light distribution property is required. Some Literatures describe configurations to widen a light distribution property, although the configurations are not directed to backlight sources of liquid crystal display panels.
Patent Literature 1 describes a conventional art example of an LED package 30 including an LED chip 38, a lens 32 with a vertical sidewall 35, and a funnel-shaped upper surface 37 (FIG. 20).
The LED package 30 has two main light paths via which light travel in the LED package 30. Light traveling via a first light path P1 is desirably light emitted from the LED chip 38. This light travels to the upper surface 37 where the light changes its traveling direction at approximately 90 degrees with respect to a vertical axis due to total inner reflection (TIR) so that the light goes out of the LED package 30 via the sidewall 35. Light traveling in a second light path P2 is light emitted from the LED chip 38 toward the sidewall 35 at an angle which causes total inner reflection of the light on the sidewall 35, or light reflected by the sidewall 35 and goes out of the LED package 30 at an angle which is far from being perpendicular to the vertical axis. The light traveling via the second light path P2 is not a desirable one, which limits an efficiency of obtaining light from the sidewall 35.
An object of the LED package 30 is efficiently obtaining light from the sidewall 35, and is not necessarily equal to an object of the present invention which will be explained later. Further, Patent Literature 1 does not detail the lens 32 with the vertical sidewall 35 and the funnel-shaped upper surface 37.
Another Literature describing use of an LED similarly with Patent Literature 1 is Patent Literature 2, which discloses a planar-mounted LED designed to have a wide directivity. Further, Patent Literature 3 discloses a light source, a light guide body, and a planar light emitting device, each of which is applicable to railway signal lamps, traffic signal lamps, large displays, automobile tail lamps etc.